The present invention relates to a prosthetic implant device, and more particularly to such implants including grooved or textured surfaces. This invention is particularly suitable for use as a hip stem implant, although is not limited thereto.
Heretofore, various types of grooved, textured or porous surfaces have been incorporated into prosthetic implants. Implants are often typically affixed into bone with a grouting material, such as polymeric bone cement. In such cases, various types of grooves, texturing or porous outer surfaces enhance the bond or securing between the bone cement and the prosthesis. Other times, implants are put in without bone cement. In these cases, it is typically desirable to provide a close, tight fit between the portion of the prosthesis to be embedded in the bone and the prepared bone surface. This tight fit is provided to stabilize the prosthesis in its proper location in the bone. With many such porous or grooved or textured surfaces implanted without bone cement, after a period of time, bony ingrowth of the contacting bone surfaces occurs in and around the porous, grooved or textured surfaces to biologically affix or further secure the implant in the bone. Often, such tight fitting implants which are utilized without a grouting material such as bone cement, are referred to as press-fit implants.
The following U.S. Patents disclose prosthetic implants which include an elongated stem, each with a plurality of substantially parallel grooves which extend longitudinally and substantially in the direction of the longitudinal axis of the stem: U.S. Pat. No. 4,430,761 to Niederer et al, U.S. Pat. No. 4,404,693 to Zweymuller, U.S. Pat. No. 3,816,854 to Schlein, and U.S. Pat. No. 2,718,228 to Van Steenbrugghe. Such grooved stems as these, if used as press-fit stems, can obtain bone ingrowth in the grooves; however, their means of transferring stress to bone is primarily through shear or sliding. Bone can transmit and accept compressive forces of significantly greater magnitude than shear forces and thus, by providing a means for compressive stress transfer to the bone (as accomplished by the present invention), the long-term fixation stability of the stem will be enhanced.
U.S. Pat. No. 4,530,116 to Frey discloses a hip stem which includes dimples or indents over the surface of the stem, while U.S. Pat. No. 4,068,324 to Townley et al discloses a hip stem which includes projecting steps.
In addition, various types of porous surfaces have been included on prosthetic implants to either enhance the securement between the bone cement/prosthesis interface when used with cement, or when used without cement or the like, the porous surfaces promote the ingrowth of bone to enhance the secure fixation of the prosthesis to the bone. U.S. Pat. No. 4,536,894 to Galante et al discloses a hip prosthesis including porous fiber metal pads on its fixation surface, while European Patent EP No. 0 128 036 to Kenna discloses a hip stem including a porous beaded fixation surface.